1. Field of the Invention
The present invention relates generally to a rotary handle operated door lock formed from a relatively small number of operating components that interact in particularly advantageous ways to selectively permit and prevent rotary latching and unlatching movements of an operating handle and a latching arm. More particularly, the invention relates to a door lock having a rotatable handle for pivoting a shaft-mounted latching arm between latched and unlatched positions, with a key operated locking system being provided for releasably retaining the rotatable components of the lock in their latched and unlatched positions.
2. Prior Art
Many proposals have been made for various types of door locks having flush mountable housings, for door locks having rotary operating handles that serve to rotate latching arms between latched and unlatched positions, and for door locks having operating handles that are nestable within recesses that are defined by associated housings. Despite such proposals, a need has remained for a flush mountable door lock having a rotatable operating handle for pivoting a latching arm between latched and unlatched positions, with a key-operated locking system being provided to releasably retain rotatable components of the lock in their latched and unlatched positions, with the operating handle being nestable within a housing recess when the operating handle is in its latched and unlatched positions, and with the lock being formed from a minimal number of easily assembled parts that interact in advantageous ways to aid in securely preventing the operating handle and the latching arm from rotating both when the lock is "locked" and "unlocked."
To the degree that prior proposals have addressed the need for such a lock, such proposals often have resulted in locks of unduly complex construction with attendantly high costs of manufacture. A further drawback of some previously proposed lock assemblies is that they have employed components which are insufficiently rugged to withstand the type of abuse to which such locks are subjected, especially when unauthorized entry is attempted. Still another drawback of many prior proposals has resulted from an insufficiently effective interaction of the lock components when "locked" to prevent the action of the lock from being defeated by overpowering it with force.
While a variety of nestable operating handles are known for use with locks, one well accepted assembly of a nestable T-shaped handle, shaft and housing has been sold by Eberhard Manufacturing Company of Cleveland, Ohio 44136 under the product designation 5630A. A key-locking version of this product has also been offered under the product designation 4874.